It is known in the building construction industry to use any one of three types of insulation materials. These may be categorized by structure as being either loose fill-type, rigid panel type, or a flexible type commonly sold in blankets or batts which may be stored in rolls and cut to desired length at the installation site.
This last category, insulation batting, is the most common type used for insulating the walls and roof of home dwellings and other commercial structures. The insulation batt usually comprises a foil or kraft paper facing with a layer of low density fiberglass adhered thereto. The facing can provide a vapor barrier, a radiant energy reflector, and also a convenient means for attaching the insulation to structural components of the building. The layer of fiberglass insulation provides most of the insulating properties of the material which are generally expressed as an "R-value". The R-value is commonly dependent on a combination of either the depth of the insulation and/or its density. The thicker and more dense the insulating material, the greater its insulating capacity and hence the greater its R-value.
While numerous attempts have been made to increase the overall insulation performance in structures by using these three insulating methods, drawbacks include significantly increased cost due to the products themselves, the additional building materials required to use the products, and greater labor costs due to additional steps required in construction. The most economical form of insulation is the insulation batting or blanket. This material has the advantages of ease of handling, flexibility, fire resistance, and low cost. Unfortunately, it has a rather low R-value.
The prior art which most closely resembles the present invention is that of multiple reflective low emissivity insulation. The use of this type of insulation in the past has been restricted to very high temperature or very low temperature applications, such as cryogenics, and provides effective insulation across extreme temperature gradients. Furthermore, these prior technologies require the use of a great number of low emissivity layers, as many as 100 per inch. In addition, these insulating systems require that the space between reflective layers be evacuated in order to eliminate heat transfer by conduction or convection. Often they include a spacer material between the reflective layers in order to prevent the layers from contacting each other and thereby creating "thermal bridges". These systems have also included the insertion of radiant energy absorbing and refracting material into the evacuated space between the reflective layers in order to further reduce heat transfer by radiation. Insulating systems of this type are described in U.S. Pat. Nos. 3,124,853 and 3,151,364 to P. E. Glaser et al. Naturally, the requirements of these systems for evacuating the spaces between reflective layers is not practical for building structures.
There are some products available for building structures which utilize a number of reflective layers with an air space between the layers. However, these systems are only effective in retarding heat transfer due to radiation. Heat transfer due to conduction and convection are allowed to occur freely by movement of air molecules between the reflective layers. The relatively low R-value of these systems, along with the specialized installation techniques involved, have restricted their widespread use in building structures.
Additionally, there are insulation products which employ a single layer of low heat conductivity material, such as foam or fiberglass, along with a reflective material adhered to both sides of the low heat conductivity material. These reflective layers are used primarily as a vapor shield, although they will improve the R-value of the insulated area if used in conjunction with an adjacent air space.
One of the main benefits of the present invention is that it utilizes commonly available building materials in its construction. There is no suggestion in any prior art teachings that a multiple layering principle, which uses common fiberglass and foil materials, would be of any advantage whatsoever for thermal building insulation. In fact, the prior art teaches just the opposite. It is common practice that if one were to add additional insulating batts to existing insulation that already include a vapor shield, the vapor shield on the added batt must be removed or slashed before installing. Additionally, the prior art teaches that for a multiple-foil layer insulation to be effective, there must be an air space between the layers and that for optimum performance these spaces should be evacuated.